Mozilla Messaging has release the sixth update for Thunderbird 3.0 on July 20th. The new Thunderbird 3.0.6 update includes several security and stability updates [Thunderbird release notes]. Thunderbird 2.0 and older users should upgrade by downloading Thunderbird 3.0.6 directly here. Thunderbird 3.0.5 users should be prompted to update within the next 48-hours or can do so manually via Help >> Check For Updates…Source:Mozilla Developers News

Mozilla Messaging has release Thunderbird 3.1 based on the Gecko 1.9.2 platform, was built by a community of passionate contributors, experienced developers, security experts, localization and support communities, and thousands of active testers.
Some of the new features:

Mozilla Messaging has release the fifth update for Thunderbird 3.0 on June 17th. The new Thunderbird 3.0.5 update includes several security and stability updates [Thunderbird release notes]. Thunderbird 2.0 and older users should upgrade by downloading Thunderbird 3.0.5 directly via http://getthunderbird.com. Thunderbird 3.0 users should be prompted to update within the next 48-hours or can do so manually via Help >> Check For Updates…Source:Mozilla Developers News